Aquarius L-Band Microwave Radiometer: 3 Years of Radiometric Performance and Systematic Effects

The Aquarius L-band microwave radiometer is a three-beam pushbroom instrument designed to measure sea-surface salinity. Results are analyzed for performance and systematic effects over three years of operation. The thermal control system maintains tight temperature stability promoting good gain stability. The gain spectrum exhibits expected orbital variations with noise appearing at longer time periods. The on-board detection and integration scheme coupled with the calibration algorithm produce antenna temperatures with NEDT for 1.44-s samples. Nonlinearity is characterized before launch and the derived correction is verified with cold-sky calibration (CSC) data. Finally, long-term drift is discovered in all channels with 1-K amplitude and 100-day time constant. Nonetheless, it is adeptly corrected using an exponential model.